In this Agda file,
I give an introduction to Lawvere theories and Monads. It's not exactly a
"gentle" introduction because:

I'm still trying to grok these things myself,

I've to live up to my reputation of writing unfathomable gagaposts.

We'll start with the State monad and, briefly, a Tick monad. The
game is the following: I'll present them syntactically -- through a
signature -- and semantically -- through a collection of
equations. I'll then show how the usual monad is related to this
presentation.